n=int(input())
s=input()

r = s.count('R')

ans=0
for i in range(r):
    if s[i]=='W':
        ans+=1

print(ans) n=int(input()) n int(input()) int input() input s=input() s input() input r = s.count('R') r s.count('R') s.count s count 'R' ans=0 ans 0 for i in range(r):
    if s[i]=='W':
        ans+=1 i range(r) range r if s[i]=='W':
        ans+=1 s[i]=='W' s[i] s i 'W' ans+=1 ans 1 print(ans) print ans s=input() input() s ans+=1 1 ans ans=0 0 ans n=int(input()) int(input()) n r = s.count('R') s.count('R') r
n=int(input())
s=input()

r = s.count('R')

ans=0
for i in range(r):
    if s[i]=='W':
        ans+=1

print(ans)